This means: can't you see that fresh water resources like the Yellow River are a gift from heaven? You can't make good use of it. When it enters the sea, it can no longer be potable fresh water! It can be seen that Comrade Lao Li has long realized the importance of fresh water resources, and he regrets that he can't make good use of such resources, so he has to drown his sorrows in wine.
Comrade Lao Li used such a magnificent poem to describe the loss of fresh water resources and warned future generations, but the latter did not know what it meant, which really made us ashamed.